(Anglais) This paper presents a mixed method to determine a 1-D three-layer wall having the same static and dynamic behaviours as a multidimensional thermal bridge. It is based on the calculations of thermal resistance, heat capacity, structure factors and an objective function using harmonic heat fluxes features. This mixed method is applied to three 2-D details. The heat flux through inner surface is analysed over time for a step solicitation and for given boundary conditions: a sinus evolution of the inside temperature and a severe or a more realistic evolution of the outside temperature. Results are really satisfactory, evolution of heat flux through the thermal bridge is close to that of the corresponding equivalent wall. For an outside temperature profile (Te) close to real data, the error on integral value of heat flux is less than 1% in each case. The results for equivalent walls are significantly better than for a classic 1-D evaluation: for a severe evolution of Te the average error is 6 to 28 times lower in the tested cases.